U.S. patent application number 09/731569 was filed with the patent office on 2001-04-19 for electrical resistor with at least two connection contact pads on a substrate with a least one recess, and process for its manufacture.
Invention is credited to Dietmann, Stefan, Ullrich, Karlheinz, Wienand, Karlheinz.
Application Number | 20010000298 09/731569 |
Document ID | / |
Family ID | 7880846 |
Filed Date | 2001-04-19 |
United States Patent
Application |
20010000298 |
Kind Code |
A1 |
Wienand, Karlheinz ; et
al. |
April 19, 2001 |
Electrical resistor with at least two connection contact pads on a
substrate with a least one recess, and process for its
manufacture
Abstract
A temperature-dependent measuring resistance with low mass and
thereby rapid response time has a conductor path provided with at
least two connection contact pads. The conductor path is applied to
a metal substrate with an insulation layer (membrane) situated
thereon. A portion of the conductor path spans a recess of the
substrate in a bridge-like manner. The conductor path is
selectively covered by a passivation layer up to its connection
contact pads.
Inventors: |
Wienand, Karlheinz;
(Aschaffenburg, DE) ; Ullrich, Karlheinz;
(Gross-Umstadt, DE) ; Dietmann, Stefan; (Hanau,
DE) |
Correspondence
Address: |
AKIN, GUMP, STRAUSS, HAUER & FELD, L.L.P.
ONE COMMERCE SQUARE
2005 MARKET STREET, SUITE 2200
PHILADELPHIA
PA
19103
US
|
Family ID: |
7880846 |
Appl. No.: |
09/731569 |
Filed: |
December 7, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09731569 |
Dec 7, 2000 |
|
|
|
09396186 |
Sep 14, 1999 |
|
|
|
Current U.S.
Class: |
338/25 ; 338/22R;
338/309; 374/E7.022 |
Current CPC
Class: |
G01K 7/183 20130101 |
Class at
Publication: |
338/25 ; 338/309;
338/22.00R |
International
Class: |
H01C 003/04; H01C
007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 1998 |
DE |
198 41 929.5 |
Claims
We claim:
1. An electrical resistor, particularly a temperature-dependent
measuring resistance with low mass and thereby rapid response time,
comprising an electrical conductor path (4) having at least two
connection contact pads (7, 8) and arranged on an electrically
insulating surface of a substrate (1), wherein the substrate (1)
has at least one recess (6) therein and a portion of the conductor
path (4) spans the at least one recess (6) in a bridge-like manner,
the conductor path (4) being arranged in a plane, wherein the
substrate (1) is made of metal and is provided with an applied
insulation layer as a membrane (3), and wherein the conductor path
(4) is arranged on the membrane (3).
2. The electrical resistor according to claim 1, wherein the
conductor path (4) is selectively covered by a passivation layer
(5) up to the connection contact pads (7, 8).
3. The electrical resistor according to claim 1, wherein the
substrate (1) has a thickness of about 0.15 mm to 0.6 mm.
4. The electrical resistor according to claim 3, wherein the
thickness is about 0.2 to 0.25.
5. The electrical resistor according to claim 1, wherein the metal
comprises an iron-nickel alloy.
6. The electrical resistor according to claim 5, wherein the alloy
comprises FeNi42 (alloy 42).
7. The electrical resistor according to claim 1, wherein the metal
comprises an iron-nickel-cobalt alloy.
8. The electrical resistor according to claim 7, wherein the alloy
comprises FeNi28Co18 (VACON 10).
9. The electrical resistor according to claim 1, wherein the metal
comprises steel 1.4767 (FeCr20A15).
10. The electrical resistor according to claim 1, wherein the metal
comprises steel 1.4541.
11. The electrical resistor according to claim 1, wherein the metal
comprises steel 1.4571.
12. The electrical resistor according to claim 1, wherein the metal
comprises nickel.
13. The electrical resistor according to claim 1, wherein the
electrical conductor path is applied on a plate-shaped membrane at
least partially covering the recess, wherein the membrane comprises
a material selected from the group consisting of SiO, MgO, ZrO,
Si.sub.3N.sub.4, TiO.sub.2, Al.sub.2O.sub.3, and mixed oxides
thereof, and the membrane has a thickness of about 0.5 to 10
.mu.m.
14. The electrical resistor according to claim 13, wherein the
thickness is about 2 to 2.5 .mu.m.
15. The electrical resistor according to claim 13, wherein the
membrane is constructed sandwich-like from a combination of the
materials.
16. The electrical resistor according to claim 1, wherein the
conductor path (4) comprises a platinum layer having a thickness of
about 0.1 to 6 .mu.m.
17. The electrical resistor according to claim 16, wherein the
thickness is about 0.3 to 0.6 .mu.m.
18. The electrical resistor according to claim 1, wherein the
passivation layer (5) comprises an SiO layer or an Al.sub.2O.sub.3
layer having a thickness of about 0.3 .mu.m to 10 .mu.m.
19. The electrical resistor according to claim 1, further
comprising an etching stop layer (2) applied to the metal
substrate, wherein the etching stop layer (2) has a thickness of
about 0.1 to 6 .mu.m.
20. The electrical resistor according to claim 19, wherein the
thickness is about 2.5 to 3 .mu.m.
21. The electrical resistor according to claim 19, wherein the
etching stop layer (2) comprises a material selected from the group
consisting of Ti, Pt, Ni and combinations thereof.
22. The electrical resistor according to claim 19, wherein the
etching stop layer (2), membrane (3) and passivation layer (5) are
applied to the metal substrate by PVD or CVD processes.
23. A process for manufacturing an electrical resistor,
particularly a temperature-dependent measuring resistance with low
mass, having an electrical conductor path with at least two
connection contact pads arranged on an electrically insulating
surface of a rectangular prism-shaped metal substrate, wherein a
portion of the conductor path spans at least one recess of the
substrate in a bridge-like manner and the conductor path is
arranged in a plane, the process comprising providing the substrate
on its front side with a metal etching stop layer, providing the
substrate on its reverse side with a photolithographic enamel
structuring, and conducting a wet chemical free etching from the
reverse side of the substrate up to the previously applied metal
etching stop.
24. The process according to claim 23, wherein the wet chemical
free etching from the reverse side of the metal substrate up to a
metal etching stop imparts a low thermal mass to the resistor.
25. The process according to claim 24, wherein the free etching
comprises spray etching with an FeCl.sub.3 solution.
Description
BACKGROUND OF THE INVENTION
1. The invention concerns an electrical resistor, in particular a
temperature-dependent measuring resistance with rapid response
time, having a conductor path provided with at least two connection
contact pads, arranged on an electrically insulating surface of a
substrate, wherein a portion of the conductor path spans at least
one recess of the substrate in a bridge-like manner, and the
conductor path is arranged in a plane. The invention also relates
to a process for manufacturing the electrical resistor.
2. A temperature-dependent measuring resistance with rapid response
time is known from German published patent application DE 197 53
642 A1, wherein the resistor is at least partially arranged on an
electrically insulating surface of a ceramic substrate, wherein a
portion of the conductor path spans in a bridge-like manner a
recess situated in the substrate, and the remaining portion of the
conductor path is provided with connection contact pads in the edge
area of the substrate adjacent to the recess. The conductor path
comprises a platinum or a gold layer, wherein the conductor path
itself is provided with a cover layer of glass. The connection
contact pads are left exposed for the purpose of subsequent
contacting. The relatively expensive construction proves to be
problematic in this case, especially in view of the structuring of
ceramics or glass as a substrate.
3. Furthermore, a temperature sensor is known from European
published patent application EP 0 446 667 A2, which sensor has
electrically conducting conductor paths applied in meander form by
thin layer technology in a measurement window on an electrically
insulating substrate having a low radiation absorption, whose end
points are connected to a measurement device circuit. The overall
area of the conductor paths in its projection on the plane of the
substrate amounts to a 20% coverage ratio of the surface of the
measurement window, so that the conductor paths can emit absorbed
radiation without interference with other conductor paths. Either
the sum of surfaces of the measurement window and the substrate
surrounding the measurement window stands in an area ratio of
>4:1 to the edge surface bordering the substrate in the
measurement window area, or the substrate is substantially etched
away under the conductor paths in the measurement window. Then, the
cross-sectional area of the reversing bends of the conductor paths
lying on the substrate is greater than the cross-sectional area of
the conductor paths, so that a resistance action as a consequence
of the temperature of the substrate on the conductor path is
effectively prevented. With this temperature sensor, temperature
measurements in the range of -70 to +50.degree. C. are
possible.
4. Furthermore, a temperature measurement arrangement (radiation
thermometer) is known from German published patent application DE
39 27 735 A1, the arrangement having a temperature-sensitive thin
layer resistor, which is applied in meander form to a sheet of
plastic which is stretched over a hollow in the substrate material.
A circuit board or a carrier made of epoxide resin is provided as a
substrate. Such a temperature measurement arrangement, owing to the
low thermal load capacity, is only suited for use in an environment
with temperatures below 200.degree. C.
5. Still further, from German published patent application DE-OS 23
02 615, a temperature-dependent electrical resistor is known, made
of resistance material which forms a coiled conductor path as a
thin layer, which is applied to a thin sheet. The sheet, which is
made of polymeric plastic, spans with its uncoated side a recess in
a carrier element which is made of copper, for example, wherein the
recess has the same shape as the conductor path and aligns with it
in a direction perpendicular to the sheet plane. The temperature
arrangement here is one which requires a high technical expenditure
for the requisite precise coverage of conductor path and
recess.
6. From German patent DE 30 15 356 C2, it is known that electric
switches in thick layer technology are preferably manufactured on
ceramic, plate-shaped substrates by printing of pastes, whose
active substances consist of metal powders, glass or glass-ceramic
powders, or mixtures of glass and metal oxides. For manufacturing
rapidly responding sensors for temperature measurement,
temperature-sensitive thick layer resistances are applied to
self-supporting layers, which have arisen by paste screen printing
with the aid of a filler material which is gasifiable under the
effect of temperature, and which cover a subsequently formed hollow
space. Here, it is a question of a comparatively expensive
process.
7. Furthermore, from German published patent application DE 38 29
765 A1 or U.S. Pat. No. 4,906,965, a platinum temperature sensor is
known, in which a platinum resistance path with at least two ends
is applied on a surface of at least one ceramic substrate. For
manufacture, a platinum conductor path is applied in the form of a
meander zigzag pattern on the inner surface of a ceramic sheet and
subsequently shaped into a roll, wherein breaks with alignment
bridges are also provided between adjacent points of the conductor
path pattern for purposes of alignment. The ceramic substrate is
fired together with the applied platinum resistance. The platinum
resistance is made resistant to the ambient atmosphere and moisture
by sealing measures. In addition, after the alignment the passage
openings and conduits requisite for this are also sealed off by
means of ceramic coating or glass paste. The comparatively high
heat capacity proves to be problematic with such an arrangement,
which does not, without more, make possible a rapid response with
sudden temperature changes, and reproduces an exact measured value
only after completing a transition function.
8. A further embodiment of a resistor element as rapid temperature
sensor is known from German published patent application DE 38 29
195 A1. Here, the resistance element is configured as a layer
resistor made of platinum paste, which is accommodated in a bubble
made of glass ceramic, which arches over an electrically insulating
ceramic substrate. Here, the self-supporting arched resistance
layer is seen as problematic in respect to mechanical stresses,
such as shock, pressure or vibration, with applications in harsh
environments.
SUMMARY OF THE INVENTION
9. An object of the invention is to create a measuring resistance
which has the simplest construction possible, and which can be
produced using economical processes. This object is achieved in
accordance with the present invention for an electrical resistor in
that the substrate is made of metal and is provided with an applied
insulation layer as a membrane, wherein the conductor path is
arranged on the membrane.
10. The robust construction proves to be especially advantageous,
wherein particularly the security against failure or disturbance
has an advantageous effect in consumer goods applications.
11. In a preferred embodiment of the invention, the conductor path
is selectively covered by a passivation layer up to its connection
contact pads. It proves to be advantageous herein that the Pt
meander, which is manufactured by known photolithographic and PVD
processes, is thereby protected from the actions of foreign
substances from without and retains its stable resistance value for
exact temperature recording.
12. Furthermore, the substrate advantageously has a thickness in
the range of about 0.15 to 0.6 mm, preferably about 0.2 to 0.25 mm.
From this there results a particularly rapid response time.
Preferably, the metal of the substrate comprises an iron-nickel
alloy, preferably FeNi42 (alloy 42). This results in an economical
substrate. Moreover, it is possible to use a substrate made of an
iron-nickel-cobalt alloy, preferably FeNi28Co18 (VACON 10).
13. Alternatively, the metal of the substrate can comprise steel
1.4767 (FeCr20A15). It is also possible to use a substrate of steel
1.4541 or steel 1.4571. Alternatively, an electrical resistor can
be used in which the metal of the substrate comprises nickel.
14. The plate-shaped membrane, functioning as an insulation layer,
at least partially covers the recess within the substrate, wherein
the membrane comprises SiO, MgO, ZrO, Si.sub.3N.sub.4, TiO.sub.2,
Al.sub.2O.sub.3 or a mixture of these materials. The thickness lies
in the range of about 0.5 to 10 .mu.m, preferably about 2 to 2.5
.mu.m.
15. In addition, it is also possible to form the membrane
sandwich-like from a combination of the previously named oxides or
oxide mixtures. Such a sandwich-like configuration has the
advantage that it can be constructed to be especially stable
against thermal and mechanical stresses.
16. The conductor path preferably comprises a platinum layer having
a thickness in the range of about 0.1 to 6 .mu.m, preferably about
0.3 to 0.6 .mu.m. Owing to the slight thickness of the platinum
layer, there results very little thermal inertia, so that
advantageously a rapid responsiveness of the sensor should be
attained. The conductor path is provided with a passivation layer
of SiO or Al.sub.2O.sub.3 to protect its surface, wherein this
layer has a thickness in the range of about 0.3 to 10 .mu.m. Owing
to the slight thickness, the rapid responsiveness also will not be
impaired.
17. In a further preferred embodiment, an etching stop layer is
applied between the substrate and membrane, which layer is
preferably made of platinum or titanium in a thickness of about 0.1
to 6 .mu.m, preferably 2.5 to 3 .mu.m.
18. The objective of the invention is achieved for a process for
manufacturing an electrical resistor, particularly a
temperature-dependent measuring resistance having a small mass,
with a conductor path which is provided with at least two
connection contact pads which are arranged on an electrically
insulating surface of a substrate, wherein a portion of the
conductor path spans at least one recess of the substrate in a
bridge-like manner, and the conductor path is arranged in one
plane, in that a substrate constructed in the shape of a
rectangular prism is provided on its front side with a metal
etching stop layer and on its reverse side with a photolithographic
enamel structuring, wherein a wet chemical free etching takes place
from the reverse side of the metal substrate up to the previously
applied metal etching stop.
19. This free etching preferably takes place by spray etching with
the aid of an FeCl.sub.3 solution, wherein the etching stop,
membrane and passivation layers are preferably applied by PVD or
CVD processes. Here, it proves to be particularly advantageous that
the known process sequences of metal structuring in the lead frame
etching art also find application here.
BRIEF DESCRIPTION OF THE DRAWING
20. The foregoing summary, as well as the following detailed
description of the invention, will be better understood when read
in conjunction with the appended drawing. For the purpose of
illustrating the invention, there are shown in the drawing
embodiment(s) which are presently preferred. It should be
understood, however, that the invention is not limited to the
precise arrangements and instrumentalities shown. In the
drawings:
21. The sole FIGURE (FIG. 1) shows in an exploded schematic
representation the structural composition of an electrical resistor
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
22. The substrate 1 comprises metal, preferably an iron-nickel
alloy, and has a thickness in the range of about 0.15 to 0.6 mm.
The alloy FeNi42 (alloy 42) with a thickness of 0.2 mm has proven
especially suitable. On this substrate, a metal etching stop 2 is
applied, preferably comprising a platinum layer or a Ti layer with
a thickness of about 2.5 to 3 .mu.m, as well as the actual membrane
layer 3, which comprises an electrically insulating material, for
example SiO, MgO, ZrO, Si.sub.3N.sub.4, TiO.sub.2, Al.sub.2O.sub.3,
or mixtures of these materials, having a thickness in the range of
about 0.5 to 10 .mu.m. Preferably, the membrane 3 has a thickness
of 2.5 .mu.m. The conductor path 4 preferably comprises a platinum
layer and has a thickness in the range of about 0.1 to 6 .mu.m,
preferably about 0.3 .mu.m to 0.6 .mu.m. The conductor path 4 is
selectively covered on its outer surface with a passivation layer
5, which comprises an SiO or Al.sub.2O.sub.3 layer, which has a
thickness in the range of about 0.3 to 10 .mu.m. The recess in
substrate 1 spanned by the conductor path in a bridge-like manner
is designated with the reference numeral 6. The recess is
preferably constructed as a through passage, i.e., window-like.
23. The connection contact pads 7, 8 are left free for an
electrical contacting after this process and are not covered by the
passivation layer 5.
24. The etching stop layer 2 applied between the substrate and the
membrane layer 3 can also be dispensed with for special uses. In
this case, the membrane layer 3 itself assumes the function of the
actual etching stop layer.
25. The low thermal mass of the resistor usable as a sensor is
effected by a wet chemical free etching from the reverse side of
the substrate 1 up to the metal etching stop, wherein the free
etching takes place by spray etching with an FeCl.sub.3 solution.
For this purpose, a photolithographic enamel structuring of the
reverse side of the metal substrate 1 takes place beforehand in
accordance with the known prior art.
26. In accordance with FIG. 1, the passivation layer 5 is situated
on the structured conductor layer 4. The passivation layer 5
comprises an electrically insulating material and is preferably
applied to the conductor path 4 by a PVD or CVD process. The
passivation layer 5 is preferably made of aluminum oxide. However,
it is also possible to use a passivation layer made of silicon
oxide. The passivation layer 5 is applied to the structured
conductor layer 4 such that the connection contact pads remain
free.
27. It will be appreciated by those skilled in the art that changes
could be made to the embodiment(s) described above without
departing from the broad inventive concept thereof. It is
understood, therefore, that this invention is not limited to the
particular embodiment(s) disclosed, but is intended to cover
modifications within the spirit and scope of the present invention
as defined by the appended claims.
* * * * *